The so-called Baeyer-Villiger oxidation or the epoxidation of olefins is a type of reaction well documented in the prior art. Amongst the different primary oxidants which may be used in these two type of reactions, the most attractive is H2O2. However, when H2O2 is used, it is necessary to add a catalyst capable of generating an active species.
The catalysts used in the processes reported in the prior art, and which use H2O2 as oxidant, are either a heavy-metal derivative, e.g. a salt, complex, silicate or oxide, or a percarboxylic acid derivative, or a precursor of said acid derivative such as a mixture of a nitrile, carboxylic acid or carboxylic anhydride or chloride with H2O2. By the expression “heavy-metal” we mean here metals other than the alkaline or alkaline earth metals.
As example of such known processes, one may cite the one described by S. Ueno et al. in Chem. Commun., 1998, 295, wherein olefins are epoxidized in the presence of H2O2, hydrotalcite (Mg10Al12(OH)24CO3) and benzonitrile. Or alternatively, one can cite A. M. d'A. Rocha Gonsalves et al. in J. Chem. Research., 1991, 208, wherein olefins are epoxidized by using a buffered solution of a percarboxylic derivative. More recently, M. C. A. van Vliet et al. in Green Chemistry, 2001, 243 described an epoxidation process using alumina as catalyst.
The disadvantage of such prior art processes resides in the fact that, at the end of the reaction, an important work-up procedure is required to eliminate said catalysts which are frequently toxic and pollutant. The final result of such work-up is the formation of important amounts of waste materials which may represent a potential threat for the environment. Furthermore, said work-up may result in the opening, i.e. degradation, of important amounts of the desired lactone or epoxide with the result of a loss of efficiency in the overall process.
There is therefore a need to develop industrial processes for performing Baeyer-Villiger reactions, as well as epoxidations of olefins, which are more environment friendly, e.g. of the so-called “green-chemistry” type.